Creating a more realistic idealized supercell thunderstorm evolution via incorporation of base-state environmental variability

Abstract

Convective environments are known to be heterogeneous in both time and space, yet idealized models use fixed base-state environments to simulate storm evolution. Recently, the base-state substitution (BSS) technique was devised to account for environmental variability in a controlled manner while maintaining horizontal homogeneity; BSS involves updating the background environment to reflect a new storm-relative proximity sounding at a prescribed time interval. The study herein sought to assess the ability of BSS to more realistically represent the structure and evolution of an observed supercell thunderstorm in comparison to simulations with fixed base-state environments. An extended dual-Doppler dataset of an intensifying supercell thunderstorm in a varying inflow environment was compared to idealized simulations of the same storm; simulations included those with fixed background environments, as well as a BSS simulation that incorporated environmental variability continuously via tendencies to the base-state variables based on changes in a series of observed soundings. While the simulated supercells were generally more intense than what was measured in the observations, broad trends in reflectivity, vertical velocity, and vertical vorticity were more similar between the observed and BSS-simulated supercell; with a fixed environment, the supercell either shrunk in size and weakened over time, or grew upscale into a larger convective system. Quantitative comparisons examining distributions, areas, and volumes of vertical velocity and vorticity further confirm these differences. Overall, BSS provides a more realistic result, supporting the idea that a series of proximity soundings can sufficiently represent the effects of environmental variability, enhancing accuracy over fixed environments.